Height control system for a hydrofoil watercraft

ABSTRACT

A height control system for a hydrofoil watercraft. Lift hydrofoils adjacent the forward portion of the watercraft are coupled to a superjacent control hydrofoil which normally rides at the surface of the water. The lift of the lift hydrofoils acts through the coupling to urge the control hydrofoil toward an increased angle of attack upon emergence of the control hydrofoil from the water. The center of lift of the control hydrofoil is located rearwardly of its pivot axis whereby its angle of attack decreases as the lift it develops increases during progressive submergence in the water. These changes cause compensating changes in the angle of attack of the lift hydrofoils.

[ Dec. 30, 1975 I 4] HEIGHT CONTROL SYSTEM FOR A HYDROFOIL WATERCRAFT [75] Inventor: David J. Cline, Brea, Calif.

[73] Assignee: Dynafoil, Inc., Newport Beach,

Calif.

22 Filed: Feb. 14,1974

21 Appl.No.:442,613

[52] U.S. Cl. ll4/66.5 H [51] Int. Cl. B63B 1/28 [58] Field of Search 114/665 H [56] References Cited UNITED STATES PATENTS Primary ExaminerTrygve M. Blix Assistant ExaminerCharles E. Frankfort Attorney, Agent, or Firm-Fulwider, Patton, Rieber, Lee & Utecht [57] ABSTRACT A height control system for a hydrofoil watercraft. Lift hydrofoils adjacent the forward portion of the watercraft are coupled to a superjacent control hydrofoil which normally rides at the surface of the water. The lift of the lift hydrofoils acts through the coupling to urge the control hydrofoil toward an increased angle of attack upon emergence of the control hydrofoil from the water. The center of lift of the control hydrofoil is located r'earwardly of its pivot axis whereby its angle of attack decreases as the lift it develops increases during progressive submergence in the water. These changes cause compensating changes in the angle of attack of the lift hydrofoils.

5 Claims, 4 Drawing Figures 29,084 US, Patent Dec. 30, 1975 3,9

HEIGHT CONTROL SYSTEM FOR A HYDROFOIL WATERCRAFT CROSS REFERENCE TO RELATED APPLICATION This application discloses a height control system particularly adapted for use in connection with the hydrofoil watercraft disclosed in my U.S. Pat. No. 3,804,048, issued Apr. 16, 1974 and entitled Hydrofoil Watercraft.

BACKGROUND OF THE INVENTION 1. Field of the Invention:

The present invention relates to a height control system for a hydrofoil watercraft, and more particularly to such a system which controls the watercraft height according to changes in the lift developed by a control hydrofoil riding at or near the water surface.

2. Description of the Prior Art:

In the operation of a hydrofoil watercraft, height above the water surface must be controlled to keep the main lift foils from rising out of the water and, at the opposite extreme, to prevent the craft from crashing into the water. Such control is usually achieved by adjusting the lift developed by the hydrofoils.

When the hydrofoils are of the completely submerged type, as compared with ladder types or surfacepiercing types, lift is normally adjusted by varying the angle of attack of the hydrofoil or, in some instances, by varying the angle of attack of a flap at the trailing edge of the hydrofoil. Consequently, by converting deviations from a desired height into compensating changes in the angle of attack of the hydrofoils the craft can be maintained at or near the desired height.

Heretofore, relatively complex hybred electromechanical systems have been proposed to continuously monitor deviations from a desired height by sensing changes in acceleration or changes in position of the craft. Such systems are quite expensive, require continuous maintenance, and are not completely reliable.

Other systems of the prior art utilize drag vanes which develop greater drag as the height of the craft decreases. The increased drag effects a movement of the drag vanes which causes the hydrofoils to move to a greater angle of attack to thereby raise the craft. The inherent drag of such a system imposesan undesirable penalty upon the performance of the watercraft. Analogous prior art systems employ floats supported in advance of the watercraft in position to drag or skim over the water surface. Through suitable interconnections between the floats and the hydrofoils, the angle of attack of the hydrofoils is changed according to changes in height by the floats relative to the water. Aside from the objectionable structural awkwardness and stresses characterizing such forwardly projecting feeler floats, the system does not sense the height of the craft relative to the water, but rather the relative height of the floats. That is, an immediate adjustment of the hydrofoils to move the floats toward the proper height does not necessarily move the watercraft toward its desired height since the character of the wave fronts at the two locations is often drastically different.

SUMMARY OF THE INVENTION According to the present invention, there is provided a watercraft height control system which utilizes control hydrofoil means located above the lift hydrofoils at the forward portion of the craft, and pivotally mounted to the same strut means which pivotally supports the lift hydrofoils. The control hydrofoil is adapted to ride upon and, intermittently, at a location slightly or partially below the water surface to thereby sense the height of the craft relative to the water surface in the immediate vicinity of the lift hydrofoils.

The control hydrofoil is mechanically interconnected to the lift hydrofoils and is characterized by a center of lift and center of gravity located behind its pivot axis. This causes the control hydrofoil to increase its angle of attack as it moves upwardly relative to the water surface, and decrease its angle of attack as it contacts and moves toward the water. The lift hydrofoils are freely pivotal and are characterized by a center of lift which is located rearwardly of the pivot axis. The mechanical interconnection of the control hydrofoil to the main or lift hydrofoils causes an opposite or compensating movement of the lift hydrofoils so that the craft tends to become stabilized or reach a state of dynamic equilibrium at some predetermined height above the water.

The present height control system is relatively straightforward in design, is comparatively easy to maintain, and utilizes a control hydrofoil which provides some degree of lift. Consequently, operation of the control hydrofoil does not involve a severe drag penalty on the performance of the watercraft. Also, as will be seen, the present system employs a means for pivotally mounting the hydrofoils which is characterized by relatively low friction operation whereby the system is sensitively responsive to changes in height of the watercraft.

Other objects and features of the invention will become apparent from consideration of the following description taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side-elevational view of a height control system, according to the present invention, mounted to the forward supporting strut of a hydrofoil watercraft;

FIG. 2 is a front elevational view of the structure of FIG. 1;

FIG. 3 is an enlarged view taken along the line 3-3 of FIG. 2; and

FIG. 4 is an enlarged view taken along the line 44 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, there is illustrated a height control system according to the present invention and comprising a supporting strut means or fin 10 which extends generally downwardly from the forward portion of a hull I2 of a hydrofoil watercraft, such as the watercraft disclosed in my aforementioned U.S. Patent Application Ser. No. 341,682, filed Mar. I2, 1973. The fin 10 is illustrated in foreshortened form and, for brevity, only a portion of the hull I2 is disclosed. It will be understood, of course, that the hull I2 is provided with supporting hydrofoils at its opposite extremities, and that the fin I0 is the forward foil supporting structure.

The major dimension of the fin 10 extends fore-andaft between a leading edge 14 and a trailing edge 16, the transverse dimension of the fin being relatively small whereby the fin 10 is characterized by a generally streamline shape.

As best seen in FIGS. 3 and 4, the fin includes a central plate 18 disposed or sandwiched between facing plates 20. Although not illustrated in detail, the leading edge 14 is preferably formed of a tough, plastic material and is characterized by a forwardly disposed portion and a downwardly disposed portion, the sides of flanks of such portions smoothly fairing into the adjacent outer surfaces of the facing plates 20. The inner, central portion of the edge 14 is slotted (not shown) to receive the blunt adjacent edge of the central plate 18, the plate 18 and edge 14 being secured together in any suitable manner, such as by an adhesive or by machine screws or the like (not shown).

The facing plates 20 are secured to the control plate 18 by a plurality of usual threaded bolts 22.

The facing plates 20 are provided in their lower portions with a pair of transversely aligned circular openings 24, and in their upper portions with similar openings 26. An opening 28 is also provided in the lower portion of the center plate 18 in axial alignment with the openings 24, but of smaller diameter. Likewise an opening is provided in the upper portion of the plate 18 concentric with the openings 26 in the facing plates 20 and of a smaller diameter than the openings 26. The openings in the lower portions of the plates 18 and 20 have a common transverse axis defining a lower or lift axis 30, while the upper openings have a common transverse axis defining an upper or control axis 32.

A circular disc or rocker element 34 having a pieshaped cut-out sector 36 is positioned within the lower opening 28 with generous clearances between its eircumference and the adjacent walls of the opening 28 so that it is freely pivotable. The apex of the sector 36 is coincident with the lift axis 30 and pivotally rests upon a pivot edge defined by the narrow inner extremity of an elongated, radially oriented bearing pivot 38. The outer extremity of the pivot 38 is fixedly mounted within a slot provided in the central plate 18 adjacent the opening 28. The rocker element 34 is thus easily pivotable about the pivot 38 with virtually no frictional constraint. Such an arrangement is particularly suited for a marine environment in which conventional bearings quickly become clogged and inoperative through corrosion, salt water encrustation, and the like.

As best seen in FIG. 4, a pair of circular cheek plates 40 having flat inner surfaces and concave outer surfaces are secured by suitable threaded bolts 42 to the rocker element 34 for pivotal movement therewith. The circumferential edges of the plates 40 lie closely adjacent the openings 24, but are generously spaced, as at 44, from the adjacent portions of the central plate 18.

A plurality of cylindrical bearing plugs 46 made of low friction material, such as tetrafluoroethyelene, are received within suitable openings provided in the periphery of the lower opening 28 in the plate 18, except for a portion of the periphery which is cut away to define a rod travel portion 48, whose purpose will subsequently be explained. The outer surfaces of the plugs 46 are engaged by the inner surfaces of the cheek plates 40, facilitating pivotal movement of the cheek plates 40 about the lift axis 30.

The cheek plates 40 mount, respectively, the complemental halves of lift hydrofoil means comprising an upper lift hydrofoil 50 and a lower lift hydrofoil 52. These halves are secured to the cheek plates by suitable threaded bolts 53, as best seen in FIG. 4. The hydrofoils 50 and 52 are each preferably delta-shaped in configuration, for a number of reasons which are not critical to this disclosure, but generally to allow foreign objects and the like to move past them without becoming entangled on the leading edges.

The lift hydrofoil means could take the form of a single hydrofoil, but dual hydrofoils 50 and 52 are preferred to reduce the lateral width of the hydrofoils necessary to provide the desired lift. The double hydrofoil is more compact, which is preferable for the type of watercraft envisioned as a preferred application for the present height control system.

The center of lift of the hydrofoils 50 and 52 lies rearwardly of the lift axis 30.

A similar arrangement is provided at the control axis 32. More particularly, the upper opening 26 pivotally receives a rocker element 54 having a pie-shaped cutout sector 36 whose apex is rockable upon the inner extremity of an elongated, radially oriented bearing pivot 56. Except for a rod travel portion 58 cut out of the material of the central plate 18, the periphery of the upper opening 26 is provided with a plurality of circumferentially spaced apart recesses which receive a corresponding plurality of cylindrical bearing plugs 60 of low friction material like the plugs 46 previously described.

A pair of circular sheet plates, one of which is illustrated at 62 in FIG. 1, are secured to the rocker element 54 by a plurality of usual threaded bolts 64. Similar bolts (not shown) extend into and mount the complemental opposite halves of an upper or control hydrofoil 66. The control hydrofoil 66 is preferably anhedral and delta-shape, although other hydrofoil forms can also be used. However, the anhedral or drooping lateral edges of the hydrofoil 66 are particularly adapted for lightly engaging the water surface, shown generally at 67 in FIGS. 1 and 2, to pivot the foil 66 clockwise. Progressively greater immersion of the hydrofoil 66, as the fin 10 moves downwardly into the water, causes progressively greater pivotal movement of the foil 66, as will be seen. The center of gravity of the hydrofoil 66 is located rearwardly of the control axis 32, that is, to the left as viewed in FIG. 3, so that the hydrofoil 66 always tends to increase its angle of attack as it moves upwardly out of the water. The phrase angle of attack is intended to mean the angle between the water stream line and the chord line of the hydrofoil.

The pivotal action of the hydrofoil 66 about axis 32 is translated by mechanical interconnections into an opposite pivotal movement of the hydrofoils 50 and 52 about their axis 30. Assuming there is a counter-clockwise pivotal movement of the foils 50 and 52, their lift will be increased because there will be a corresponding increase in their angle of incidence or attack, that is, the angle between their chord lines and the water stream line. As will next be seen, their interaction of the foil 66 with the foils 50 and 52 eventually establishes a state of dynamic equilibrium in which the watercraft hull 12 is supported above the water surface 67 at a height such that the rearward lateral tips of the control hydrofoil 66 just skim or touch the top of the water 67.

It is noted that the center of lift of the hydrofoil 66 is located rearwardly of the control axis 32, which has the effect of causing a decrease in the angle of attack of the hydrofoil 66 as it is moved deeper into the water. Thus, as the fin l0 and hydrofoil 66 moves downwardly relative to the water surface 67, the hydrofoil lateral tips first engage the water surface. This pivots the hydrofoil 66 clockwise, as viewed in FIG. 3. As the hydrofoil 66 continues to move downwardly, the lift upon its surfaces gradually increases, and the rearward extremity of the hydrofoil is raised to further decrease the angle of attack of the hydrofoil 66. v

The linkage means which couple the hydrofoil. 66 to the foils 50 and 52 is operative upon pivotal movement of the control hydrofoil 66 to oppositely pivot the lift hydrofoils 50 and 52. This linkage isfitted within a cut-away portion or recess 68 provided in the plate 18 and extending generally vertically between the cutaway rod travel portions 48 and 58 which are located adjacent the pivot axes 30 and 32, respectively. This linkage means comprises a generally "horizontally oriented piv'ot arm 70 located approximately midway between the pivot axes 30 and 32and mounted at its forward extremity to one of the facing plates 20 for pivotal movement about a pivot axis 72. The opposite or rearward extremity of the arm 70 is pivotally connected to the lower extremity of an elongated, generally vertical extending upper actuating rod or arm 74, the upper extremity of which is threaded into a trunnion 76. The trunnion 76 is pivoted at its opposite sides within suitable recesses provided in the adjacent cheek plates 62 and is movable through the rod travel cut-out portion 58 to effect" pivotal movement of the plates 62 about the control axis 32.

An elongated, generally vertical oriented lower actuating arm 78 is pivotally mounted at its upper extremity to the pivot arm 70 between its opposite extremities. As best seen in FIG. 4, the lower extremity of the arm 78 is threaded into a trunnion 80 which is pivotally carried at its opposite extremities within suitable recesses provided in the cheek plates 40, in a manner similar to the mounting of the trunnion 76 previously described.

The arms 74 and 78 may be threaded at their ends for adjustable movement into or out of their respective trunnions 76 and 80 to thereby make adjustments in the relative positions of the associated hydrofoils. In addition, although not shown in detail, it will be apparent that the pivot point of the upper extremity of the arm 78 can be located more forwardly or more rearwardly to thereby adjust the extent of movement of the arm 78 which will occur in response to any movement of the arm 74. Another sophistication which can be added, as will be obvious to those skilled in the art, are suitable attenuation means, such as a dashpot or the like (not shown), to render the hydrofoils 50 and 52 less sensitive to the movements of the control hydrofoil 66. Such attenuation means could conveniently be incorporated anywhere in the mechanical linkage between the foil 66 and the foils 50 and 52.

DESCRIPTION OF OPERATION As previously indicated, where submerged hydrofoils such as the hydrofoils 50 and 52 are employed in a hydrofoil watercraft, it is necessary that their lift be adjustable to maintain the watercraft at a desired height above the water surface 67. In the present system this is done by adjustment of the angle of attack.

The hydrofoils are in a state of dynamic equilibrium with the control hydrofoil 66 at a relatively high angle of attack and the foils 50 and 52 nearly horizontal, as illustrated in FIG. 3. Assuming that a wave front is encountered, or there is some other disturbance of the state of equilibrium tending to move the fin downwardly relative to the water surface 67, the lateral tips Then as submergence of the foil 66 continues, the foil 66 is gradually pivoted inv a clockwise direction, as .viewed in FIG 3,.reducing its angle of attack. .The foil 66 carries the actuating arm 74 upwardly, which moves the arm 78 upwardly, and this pivots the hydrofoils 50 and.52 in a counterclockwise direction about the lift axis 30. Such pivotal movement increases the angle of attack of the foils 50 and 52, which increases the lift they generate, and consequently the fin 10 moves upwardly to establish the watercraft at a height at which dynamic equilibrium is again achieved.

An opposite action occurs when the watercraft tends to rise to too great a height relative to the water surface 67, as when a wave trough is encountered. In such a casethe location of the center of gravity of the control foil 66 causes it to pivot in a counterclockwise direction as it rises out of the water. This increases its angle of attack and causes movement of the arms 74 and 78 downwardly. The angle of attack and consequently the lift of the foils 50 and 52 then decreases. The watercraft then drops farther into the water until dynamic equilibrium is established.

In the present disclosure, when reference is made to an adjustment of the angle of attack of the hydrofoils 50 and 52, this is intended to comprehend the obvious equivalent of hydrofoils equipped with trailing flaps whose angles of inclination are adjustable. Such flaps could easily be made pivotable, instead of the hydrofoils, and achieve the same result of adjusting their lift, as will be apparent to those skilled in the art.

Various modifications and changes may be made with regard to the foregoing detailed description without departing from the spirit of the invention.

I claim:

1. A height control system for a hydrofoil watercraft, said system comprising:

supporting strut means including a tin extending foreand-aft and generally downwardly from the watercraft hull;

control hydrofoil means adapted to ride at or above the water surface and pivotally mounted to said fin in symmetrical relation thereto for pivotal movement about a transverse control axis, and having a center of lift and a center of gravity located rearwardly of said control axis;

lift hydrofoil means mounted to said strut means below said control hydrofoil means for pivotal movement about a transverse lift axis, said lift hydrofoil means having a center of lift located rearwardly of said transverse lift axis; and

linkage means coupling said control hydrofoil means and said lift hydrofoil means and operative upon pivotal movement of said control hydrofoil means to oppositely pivot said lift hydrofoil means, said linkage means including a pivot arm located between said control axis and said lift axis and pivoted at one extremity to said strut means; an upper actuating arm pivotally connected at its lower extremity to the extremity of said pivot arm opposite said one extremity, and pivotally connected at its upper extremity to said control hydrofoil means rearwardly of said control axis; and a lower actuating arm pivotally connected at its upper extremity to said pivot arm between the extremities thereof, and at its lower extremity to said lift hydrofoil means forwardly of said lift axis.

2. A height control system for a hydrofoil watercraft, said system comprising:

supporting strut means including a fin extending foreand-aft and generally downwardly from the watercraft hull, said fin including a lower recess and an upper recess;

1 control hydrofoil means adapted to ride at or above the water surface and pivotally mounted to said fin in symmetrical relation thereto for pivotal movement about a transverse control axis, and having a center of lift and a center of gravity located rearwardly of said control axis;

means extending into said upper recess and defining an upper pivot edge coincident with said control axis;

lift hydrofoil means mounted to said strut means below said control hydrofoil means for pivotal movement about a transverse lift axis, said lift hydrofoil means having a center of lift located rearwardly of said transverse lift axis;

means extending into said lower recess and defining a lower pivot edge coincident with said lift axis; and

linkage means coupling said control hydrofoil means and said lift hydrofoil means and operative upon pivotal movement of said control hydrofoil means to oppositely pivot said lift hydrofoil means, said lift hydrofoil means including a lower element 8 rockable upon said lower pivot edge to provide said pivotal movement of said lift hydrofoil means about said lift axis, and said control hydrofoil means including an upper element rockable upon said upper pivot edge to provide said pivotal movement of said control hydrofoil means about said control axis.

3. A control system according to claim 2 wherein said control hydrofoil means comprises an anhedral deltashape hydrofoil.

4. A control system according to claim 2 wherein said lift hydrofoil means comprises a pair of superposed hydrofoils located above and below said lift axis.

5. A control system according to claim 2 wherein said fin includes a plurality of bearing plugs made of low coefficient of friction material disposed about said upper and lower recesses; and further including an upper pair of cheek plates mounted on opposite sides of said upper recess, and a lower pair of cheek plates mounted on opposite sides of said lower recess, said upper pair of cheek plates being secured to said upper element and slidable over certain of said bearing plugs during rockable movement of said upper element, said lower pair of cheek plates being secured to said lower element and slidable over certain of said bearing plugs during rockable movement of said lower element. 

1. A height control system for a hydrofoil watercraft, said system comprising: supporting strut means including a fin extending fore-and-aft and generally downwardly from the watercraft hull; control hydrofoil means adapted to ride at or above the water surface and pivotally mounted to said fin in symmetrical relation thereto for pivotal movement about a transverse control axis, and having a center of lift and a center of gravity located rearwardly of said control axis; lift hydrofoil means mounted to said strut means below said control hydrofoil means for pivotal movement about a transverse lift axis, said lift hydrofoil means having a center of lift located rearwardly of said transverse lift axis; and linkage means coupling said control hydrofoil means and said lift hydrofoil means and operative upon pivotal movement of said control hydrofoil means to oppositely pivot said lift hydrofoil means, said linkage means including a pivot arm located between said control axis and said lift axis and pivoted at one extremity to said strut means; an upper actuating arm pivotally connected at its lower extremity to the extremity of said pivot arm opposite said one extremity, and pivotally connected at its upper extremity to said control hydrofoil means rearwardly of said control axis; and a lower actuating arm pivotally connected at its upper extremity to said pivot arm between the extremities thereof, and at its lower extremity to said lift hydrofoil means forwardly of said lift axis.
 2. A height control system for a hydrofoil watercraft, said system comprising: supporting strut means including a fin extending fore-and-aft and generally downwardly from the watercraft hull, said fin including a lower recess and an upper recess; control hydrofoil means adapted to ride at or above the water surface and pivotally mounted to said fin in symmetrical relation thereto for pivotal movement about a transverse control axis, and having a center of lift and a center of gravity located rearwardly of said control axis; means extending into said upper recess and defining an upper pivot edge coincident with said control axis; lift hydrofoil means mounted to said strut means below said control hydrofoil means for pivotal movement about a transverse lift axis, said lift hydrofoil means having a center of lift located rearwardly of said transverse lift axis; means extending into said lower recess and defining a lower pivot edge coincident with said lift axis; and linkage means coupling said control hydrofoil means and said lift hydrofoil means and operative upon pivotal movement of said control hydrofoil means to oppositely pivot said lift hydrofoil means, said lift hydrofoil means including a lower element rockable upon said lower pivot edge to provide said pivotal movement of said lift hydrofoil means about said lift axis, and said control hydrofoil means including an upper element rockable upon said upper pivot edge to provide said pivotal movement of said control hydrofoil means about said control axis.
 3. A control system according to claim 2 wherein said control hydrofoil means comprises an anhedral delta-shape hydrofoil.
 4. A control system according to claim 2 wherein said lift hydrofoil means comprises a pair of superposed hydrofoils located above and below said lift axis.
 5. A control system according to claim 2 wherein said fin includes a plurality of bearing plugs made of low coefficient of friction material disposed about said upper and lower recesses; and further including an upper pair of cheek plates mounted on opposite sides of said upper recess, and a lower pair of cheek plates mounted on opposite sides of said lower recess, said upper pair of cheek plates being secured to said upper element and slidable over certain of said bearing Plugs during rockable movement of said upper element, said lower pair of cheek plates being secured to said lower element and slidable over certain of said bearing plugs during rockable movement of said lower element. 